Micro ion pump for a low-pressure microdevice microenclosure

Abstract

A miniature ion pump, and method for fabricating the miniature ion pump, that may be included within a low-pressure microdevice microenclosure. The miniature ion pump comprises two charge plates separated by a constant distance, fabricated by well-known microchip fabrication techniques, to which a voltage potential difference is applied in order to create a perpendicular electric field that ionizes gas molecules. The resulting positively charged ions are adsorbed to charge plates, thus removing gas molecules from the interior of the low-pressure microenclosure and maintaining a low-pressure environment surrounding the enclosed microdevice.

1 . A micro ion pump included within a low-pressure microenclosure, the micro ion pump comprising: 
 a first charge plate;    a second charge plate separated from the first charge plate by a distance; and    a circuit coupled to the first charge plate and the second charge plate that establishes a voltage potential differential between the first charge plate and the second charge plate, the voltage potential differential inducing an electric field in which gas molecules within the low-pressure microelectronic device collide with electrons accelerated in the electric field to produce ions that are accelerated in a direction opposite to the electrons so that the ions adsorb to the more negative of the first and second charge plates.    
     
     
         2 . The micro ion pump of  claim 1  wherein the first charge plate is fabricated by well known microchip fabrication techniques, including metal layer deposition techniques, on an inner surface of the low-pressure microenclosure and wherein the second charge plate is fabricated by the well known microchip fabrication techniques on a surface of a microelectronic device mounted within the low-pressure microenclosure.  
     
     
         3 . The micro ion pump of  claim 3  wherein the first charge plate and the second charge plate comprise a metal layer deposited on a dielectric substrate.  
     
     
         4 . The micro ion pump of  claim 1  wherein the metal layer comprises titanium.  
     
     
         5 . The micro ion pump of  claim 1  wherein the metal layer comprises a titanium alloy.  
     
     
         6 . The micro ion pump of  claim 1  wherein the more electrically negative charge plate of the first charge plate and the second charge plate is fabricated to have surface features to increase the surface area of the charge plate.  
     
     
         7 . The micro ion pump of  claim 1  wherein the micro ion pump maintains internal pressure of the low-pressure microenclosure below 10 −4  Torr.  
     
     
         8 . The micro ion pump of  claim 1  wherein the circuit includes a current detection circuit that detects ion-induced current provided by ionized gas molecules.  
     
     
         9 . The micro ion pump of  claim 8  wherein the detected ion-induced current is related to a detected internal pressure within the low-pressure microenclosure by a pressure sensing circuit.  
     
     
         10 . The micro ion pump of  claim 8  wherein the detected internal pressure is reported on a reporting device.  
     
     
         11 . The micro ion pump of  claim 8  wherein a high detected internal pressure invokes a warning system.  
     
     
         12 . A method for maintaining a high-vacuum within a low-pressure microenclosure, the method comprising: 
 including a first charge plate and a second charge plate within the low-pressure microenclosure, the second charge plate separated from the first charge plate by a distance within the low-pressure microelectronic device microenclosure;    coupling a circuit to the first charge plate and the second charge plate; and    applying a voltage potential differential between the first charge plate and the second charge plate via the circuit, the voltage potential differential inducing an electric field in which gas molecules within the low-pressure microelectronic device collide with electrons accelerated in the electric field to produce ions that are accelerated in a direction opposite to the electrons so that the ions adsorb to the more negative of the first and second charge plates.    
     
     
         13 . The method of  claim 12  wherein the micro ion pump maintains internal pressure of the low-pressure microenclosure below 10 −4  Torr.  
     
     
         14 . A method for maintaining a high-vacuum within a low-pressure microenclosure, the method comprising: 
 including a first charge plate and a second charge plate within the low-pressure microenclosure, the second charge plate separated from the first charge plate by a distance within the low-pressure microenclosure;    coupling a circuit to the first charge plate and the second charge plate, the circuit including an ion-induced current detection circuit; and    applying a voltage potential differential between the first charge plate and the second charge plate via the circuit, the voltage potential differential inducing an electric field in which gas molecules within the low-pressure microelectronic device collide with electrons accelerated in the electric field to produce ions that are accelerated in a direction opposite to the electrons so that the ions adsorb to the more negative of the first and second charge plates, the adsorbed ions contributing an ion-induced current to the circuit that is related, in magnitude, to the pressure within the low-pressure microenclosure.    
     
     
         15 . The method of  claim 14  wherein the micro ion pump maintains internal pressure of the low-pressure microenclosure below 10 −4  Torr.  
     
     
         16 . The method of  claim 14  wherein the ion-induced current is detected by the current detection circuit and related to internal pressure within the low-pressure microenclosure in order to monitor the pressure within the low-pressure microenclosure  
     
     
         17 . The method of  claim 16  wherein, when internal pressure within the low-pressure microenclosure rises above a maximum pressure, a warning system is invoked.